LOS ANGELES » Despite the subzero temperatures and lack of oxygen, people can survive even a long journey in the wheel well of a jetliner. The latest example is a teenager who, according to authorities, stowed away on a 5 1/2-hour flight from San Jose, Calif., to Hawaii. While the number of known stowaway attempts is few, people have survived with surprising frequency.

HOW DANGEROUS ARE THE CONDITIONS?

Very. At 38,000 feet — the cruising altitude of the Hawaiian Airlines flight that the FBI says the 15-year-old took Sunday — the outside air temperature is about minus 85 degrees. The air is so thin that a person will pass out because the brain is starved of oxygen.

The plane’s own machinery can aid a stowaway’s survival, at least initially. Warmth radiating from the wheels, which heat up on the runway during takeoff, and from hydraulic fluid lines can moderate the temperature. But those effects dissipate, and at cruising altitude the temperature in the wheel well would be about minus 30 degrees, estimated John Hansman, a professor of aeronautics and astronautics at the Massachusetts Institute of Technology.

Unlike areas of the cargo hold that are pressurized so that pets can breathe, air in the wheel wells is essentially the same as outside the plane. An FBI spokesman in Hawaii said the boy told authorities he did not remember the flight.

And then there is the huge risk when the wheels are lowered for landing. This opens the equivalent of a trap door, turning a cramped but relatively sheltered space into one from which it would be easy to fall thousands of feet to the ground or water below.

Wheel well survivors typically find space in a recess area next to where the gear retracts, according to an FAA review of cases. The boy hopped into a Boeing 767, and it was not immediately clear how big the area is on that jet. Boeing representatives did not return calls seeking comment.

SO HOW CAN THE HUMAN BODY DO IT?

By entering a state akin to hibernation. Breathing, heart rate and brain activity can continue — but at a much slower-than-normal rate. Being younger helps the chances of survival, though surgeons may try to recreate this body state during surgery on older people.

Several doctors likened the body’s experience in a wheel well on a long flight to what happens when someone falls under the ice of a frozen pond. They may have no pulse when they are pulled out, but could be revived.

"When it comes to hypothermia, all bets are off," said Dr. Jay Lemery, a professor at the University of Colorado specializing in emergency medicine in the wilderness. A body shut down by extreme cold should be "presumed alive, until they are warm and dead."

HOW FREQUENTLY DO PEOPLE SURVIVE?

Worldwide, there have been 105 known people who stowed away since 1947, according to data kept by the Federal Aviation Administration. Counting the California teen, 25 made it alive, for a survival rate of about 1 in 4. The FAA notes that the rate may be lower, because people could have stowed away and fallen out of the wheel well without anyone knowing.

Prior to this case, there were two known instances when someone stowed away on a flight that took off and landed within the United States. One was in 2010, in which a teenager died on a flight between Charlotte, N.C., and Boston. The other was in 1972. There are other instances in which someone flew to the United States from another country.